The Necro Dominion keeps the dead, and it keeps the accounts on the dead. Its ships are stolen wrecks, held together and lit by void energy, which does not behave the way honest physics prefers. The hulls look like skeletons that refused the arrangement. The weapons are lances and withering fields. The shields drink some of what hits them.
The crews are vampires, necromancers, and the bound dead. No living crew has ever been taken off a captured Dominion ship. The Dominion keeps the lists anyway. Funeral debts, soul-pacts, names, rites left unfinished. The horror there is patient, and it files paperwork.
In a fight they come on hard. Small craft like bone, trailing dark. They do not drop a debt, a name, or a rite left open, and they will cross a sector to close the entry.